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Rebecca Girresch, Sara Patterson, Andrea S Bordt, James R. Anderson, James A Kuchenbecker, Jay Neitz, David W Marshak, Judith Mosinger Ogilvie; Synaptic input to parasol and smooth monostratified ganglion cells in central macaque retina. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4525.
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© ARVO (1962-2015); The Authors (2016-present)
ON parasol (PC) and ON smooth monostratified (SM) cells are two types of primate retinal ganglion cells (GCs) that are similar in many respects, including co-stratification in the innerplexiform layer (IPL), and make important contributions to motion vision perception. The goal of this study is to compare the synaptic input to these GCs in central macaque retina.
A connectome from inferior parafoveal macaque retina was generated using serial block-face scanning electron microscopy and annotated using the Viking software package. 3 PCs and 2 SMs were reconstructed and identified by their distinctive morphology. Ribbon and conventional synapses were annotated, and selected presynaptic cells were reconstructed. All bipolar cells (BCs) synapsing onto 2 PCs and one SM were annotated and classified based on: area of the axonal arbor, morphology and stratification in the IPL.
Although PCs and SMs differed dramatically in dendritic field size, they received a similar number of total synapses (~275). 2 PCs received excitatory input from an average of 55 distinct BCs and the SM received input from 49 distinct BCs; both cells received a majority of their input from diffuse BCs. Unexpectedly, giant BCs comprised ~7% of BC input to the SM, but this input varied considerably between PCs, 0% for one and 8% for the other. Midget BCs contributed ~11% of BC input to 2 PCs but only ~2% to one SM. In addition, the proportion of BC to amacrine cell (AC) input differed between these two cell types. PCs had a synaptic input ratio of 1 BC:1 AC while SM was 1 BC:3 AC. Of note, PC BC:AC ratio and proportion of wide-field AC (WFAC) input varied regionally between inferior and previously reported temporal retina (ARVO 2019, #5274). In inferior retina, the BC:AC ratio was 1:1, but in temporal retina it was 1:3. In temporal retina 6 PCs received 17% of their input from wide-field ACs, but in inferior retina, 2 PCs each received less than 1% of input from WFACs.
PCs and SMs differ in their proportion of BC:AC input and the presynaptic cell types, with SM receiving considerable input from giant BCs. Additionally, PC input varies regionally with greater excitatory BC input and considerably less WFAC input in inferior than temporal retina. Taken together, these data show PCs and SMs vary in their input despite co-stratifying, suggesting they comprise parallel but distinct visual pathways.
This is a 2020 ARVO Annual Meeting abstract.
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